“You did not say, ‘in their mouth,’ you said, ‘his or her’—because you are an educated man and you speak in the singular and not the plural: ‘his or her,’ to go with ‘each’—it is grammatically correct. Mademoiselle Jennie, she is a housemaid, but she has the speech of an educated person and the vocabulary also. She used the word ‘inevitable’ when talking about her death, her murder. And then she said to me, ‘So you see, there is no help to be had, and even if there were, I should not deserve it.’ She is a woman who uses the English language as it should be used. Therefore, mon ami . . .” Poirot was up on his feet again. “Therefore! If you are correct and Jennie meant to say, ‘Please let no one open their mouths’ in the sense of ‘Please let no one give information to the police,’ why did she not say, ‘Please let no one open his or her mouth?’ The word ‘no one’ requires the singular, not the plural!”

I stared up at him with an ache in my neck, too bewildered and weary to respond. Hadn’t he told me himself that Jennie was in a frightful panic? In my experience, people who are stricken with terror tend not to fuss about grammar.

I had always thought of Poirot as among the most intelligent of men, but perhaps I had been wrong. If this was the sort of nonsense he was inclined to spout, then no wonder he had judged it time to submit his mind to a rest cure.

“Naturally, you will now tell me that Jennie was distressed and was therefore not careful about her speech,” Poirot went on. “However, she spoke with perfect correctness apart from this one instance—unless I am right and you are wrong, in which case Jennie said nothing that was grammatically incorrect at all!”

He clapped his hands together and seemed so gratified by his announcement that I was moved to say rather sharply, “That’s marvelous, Poirot. A man and two women are murdered, and it’s my job to sort it out, but I’m jolly pleased that Jennie, whoever she is, didn’t slip up in her use of the English language.”

“And Poirot also, he is jolly pleased,” said my hard-to-discourage friend, “because a little progress has been made, a little discovery. Non.” His smile vanished and his expression became more serious. “Mademoiselle Jennie did not make the error of grammar. The meaning she intended was, ‘Please let no one open the mouths of the three murdered people—their mouths.’ ”

“If you insist,” I muttered.

“Tomorrow after breakfast you will return to the Bloxham Hotel,” said Poirot. “I will join you there later, after I look for Jennie.”